U.S. Pat. No. 3,703,450 describes a method for making a precision conductive mesh screen. First, this method constructs a mandrel. The prior-art mandrel is constructed by placing a master plate with the screen pattern on the glass substrate and by vapor depositing a thin film through the interstices of the master plate to form the screen's pattern on the glass. After removing the master plate from the glass substrate, the method deposits photoresist over the entire glass plate. Next, the method exposes and develops the photoresist to produce a layer of thin film in a screen pattern covered with a layer of photoresist in the same screen pattern. Next, the method deposits silicon monoxide on the entire glass substrate and removes the silicon monoxide and photoresist from the thin film pattern. This non-reusable mandrel is now ready for manufacturing the screen. This prior-art mandrel has several disadvantages. It cannot manufacture small geometry devices as pointed out in U.S. Pat. No. 4,549,939 discussed below. Also, the complicated prior-art process for making this mandrel has low yields.
U.S. Pat. No. 4,549,939 describes another prior-art thin film mandrel and the method of making it. This prior-art process constructs the prior-art mandrel by forming a stained pattern shield on a glass substrate and depositing a conductive and transparent thin film onto the substrate. Next, the prior-art method coats the thin film with resist and shines a light through the glass substrate and the transparent thin film to expose the unshielded photoresist. Finally, the photoresist is developed and forms the mold for electroforming. The prior-art mandrel formed by this process has several disadvantages. It is non-reusable and of poor quality due to resist broken after the electro-forming cycle. Additionally, it requires the use of a conductive thin film that is transparent; a costly and exotic material.
U.S. Pat. No. 4,528,577 describes another prior-art mandrel and the method of making it. This prior-art method of manufacturing orifice plates for thermal ink jet printheads electroforms nickel onto a stainless steel mandrel plate that contains either a pre-etched orifice pattern or a photoresist orifice pattern. Unfortunately, stainless steel mandrel plates always contain a large number of scratches and defects. These scratches and defects arise from characteristics of the stainless steel material and from the manufacturing process. The scratches and defects, which can not be eliminated, degrade the quality of the orifice plates manufactured from stainless steel mandrels. These inferior orifice plates produce inferior print quality. The method and apparatus in accordance with the present invention obviate these problems with mandrels in the prior art.